Field of the Invention
The present invention relates to a photoelectric conversion device and an image sensing system.
Description of the Related Art
Japanese Patent Laid-Open No. 2013-146045 discloses a photoelectric conversion device including pixels which output current signals in accordance with charge quantities generated by photoelectric conversion (FIG. 2 of Japanese Patent Laid-Open No. 2013-146045). Each pixel includes a photodiode and a differential amplifier. The differential amplifier includes a first input transistor and a second input transistor. A node to which charges generated by the photodiode are transferred is connected to the gate of the first input transistor. A reset voltage supply line VRES is connected to the second input transistor. The source of the first input transistor is connected to the drain of the first selecting transistor via a resistor R1. The source of the second input transistor is connected to the drain of the first selecting transistor via a resistor R2. The drain of the second input transistor is connected to an output node OUT via a second selecting transistor. A current signal corresponding to the charge quantity generated by photoelectric conversion is output from the output node OUT. In the photoelectric conversion device described in Japanese Patent Laid-Open No. 2013-146045, a digital signal corresponding to the charge quantity generated by photoelectric conversion is generated based on the current signal output from the output node OUT of the pixel.
The photoelectric conversion device described in Japanese Patent Laid-Open No. 2013-146045 incorporates the differential amplifier in each pixel. The circuit scale of each pixel increases and is not suitable for a multi-pixel arrangement.